The present invention relates generally to techniques involving optical cavities, such as techniques that sense output light from optical cavities. Such techniques can, for example, obtain sensing results that include information, such as about an analyte.
Liang X. J., Liu, A. Q., Zhang, X. M., Yap, P. H., Ayi, T. C., and Yoon, H. S., “Refractive Index Measurement of Single Living Cell Using a Biophotonic Chip for Cancer Diagnosis Applications,” 9th International Conference on Miniaturized Systems for Chemistry and Life Sciences, Oct. 9-13, 2005, Boston, Mass., 2005, pp. 464-466 describe techniques that perform refractive index (RI) measurement of single living cells using a biophotonic chip for cancer diagnosis applications. Liang et al. describe a biophotonic chip that is formed by bonding a metal-coated glass slide with a PDMS slab molded using soft lithography technology. An analysis unit embedded in the chip to measure RI includes a laser diode with one surface opposite a gold-coated mirror, forming an external laser cavity. A microlens array in the chip improves beam quality, and living cells in a buffer are driven by electrokinetic force and delivered into an analysis region along microfluidic channels. A difference in RI between a cell and the buffer changes the effective cavity length so that laser emission varies, with a wavelength shift. The cell's effective RI can be computed by monitoring wavelength and power.
Table 1 from Liang shows a number of exemplary refractive indices relevant to cancerous cells.
TABLE 1Cell TypeRefractive IndexCulture medium1.350HeLa1.392PC121.395MDA-MB-2311.399MCF-71.401Jurkat1.390
Liang et al. state that automatic measurement of RI of a living cell in real time offers low cost, high accuracy disease diagnosis.
It would be advantageous to have improved techniques for optical cavities, including improved techniques for photosensing optical cavity output light.